|
Search: id:A056258
|
|
|
| A056258 |
|
Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) - 23 for n > 0. |
|
+0
2
|
| |
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Numbers n such that (670*10^n + 23)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 4 followed by digit 7 is prime.
Numbers corresponding to terms <= 483 are certified primes. For numbers corresponding to 1485 and 1577 see P. De Geest, PDP Reference Table.
a(n) = A082712(n-1) - 2.
|
|
REFERENCES
|
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
|
|
LINKS
|
P. De Geest, PDP Reference Table
Makoto Kamada, Factorizations of 744...447.
|
|
EXAMPLE
|
74444444447 is prime, hence 9 is a term.
|
|
PROGRAM
|
(PARI) a=77; for(n=0, 1600, if(isprime(a), print1(n, ", ")); a=10*a-23)
(PARI) for(n=0, 1600, if(isprime((670*10^n+23)/9), print1(n, ", ")))
|
|
CROSSREFS
|
Cf. A000533, A002275, A082712.
Sequence in context: A147268 A147376 A101141 this_sequence A147282 A146602 A146413
Adjacent sequences: A056255 A056256 A056257 this_sequence A056259 A056260 A056261
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 18 2000
|
|
EXTENSIONS
|
Edited by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
|
|
|
Search completed in 0.006 seconds
|
